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UNITED i STATES 4PATENT OFFICE.y

WILLIAM W. Bruce, o'E WASHINGTON, DISTRICT on COLUMBIA.

AUSER AND GIMLET.

SPECIFICATION forming part of Ltters Patent No. 270,200, dated January 9, 1883.

Application filed September 29, 1882. (No model.)

Io all whom it may concern.

\ Be it known that I, WILLIAM W. BRIGG, a citizen of the United States of America, residing at Washington, in the District of Columbia, have'invented certain new and useful Improvenien ts in Gimlets and Angers, of which` the peculiar point hereinafter more fully described and claimed.

In the accompanying drawings, Figure l represents an elevation of a gimlet constructed according to my improvement; Fig. 2, a siniilar view ofthe lower part of an auger; Fig. 3, a detail representing an enlarged view` ot' a portion of the point, and Fig. 4t a section of the point enlarged.

I make the shank of my gimlet, with the channel A, in any approved manner or shape;

.but instead ot' leaving the screw-point B with' the ordinary con tinuousthread Irnakeagroove or grooves, U, from the top ofthe screw-point and communicating with the` shank-channel down to or nearly to -the extreme end of the screw. The form of this groove is more clearly shown in Figs. 3 and 4, and more particularly in Fig. 4, where it will he seen that the edge ot' the groove is undercut at a, so as to present very sharp cutting-edges to the wood. Where there are two channels in the shank, as in angers, I prefer to make two grooves down the'screw-point opening from the opposite channels in the shank; but where there is but one channel, as inthe gimlet shown in the drawings, I make but one groove across the thread ol the point. By the use ofthis groove, especially when undercut, as shown, it 1s clear `that the ends of the threads cut their way into the wood, each ot' the ends of the threads at the cutting-edge removing the particles ot' Wood in its path, and thus instead of the thread of the 'screw-pointibrcing the grain of the -wood apart,as in the ordinary ginilet, (thus tending to split the wood,) the thread of my point cuts a female thread inthe wood, and owing to the upper end ot' the groove terminating in the channel ot' the shank the particles of `Wood passing into the groove tind their Way into the channel in the shank. By making the edge of the groove undercut on one Lsideonly, as shown in Fig. 4, I leave tne face' ot thegroove on the other side full, (Where the cutting-edge Ais not needed.) whereby greater strength is obtained than it' both sides of the groove had undercut or cutting edges.

I make no claim hereto the groove running in a spiral direction across the thread ot' the point, as I intend to make a separate application for this feature of my invention.

I am aware that the old-fashioned pod-gim let has had its pod extended downward in a straight line through the screw-point; but this does not accomplish the same object as my invention, for while it is true the chips will gather into a' straight podextension, yet as the extension is perpendicular there is nothing to cause the chips to pass out of the extension channel into the shank-channel, as in my iniproved giinlet or auger.

I am also aware that an ice-auger was patented Julie l0, 1873, in which the shank-channel was continued downward beyond the shank proper; but there was no threaded or Screw point on this auger.

I do not claim broadly a tool having one edgev undercut and the other full, as I am aware that this feature is old.

What I claim as new isl A gimlet, auger, or similar tool having a spiral sha-nkchannel, A, and a screw-point,B, provided with a groove, C, forming an eXtension ot' said channel in substantially the same direction 'downward and across the thread ot' the point B, and having one edge undercut and the other full, substantially as and for the purpose set forth.

In testimony whereof I affix my signature, in presence of' two witnesses, this 26th day of beptember, 1882. t

WILLIAM W. Baise.

Witnesses: T. J. W. ROBERTSON,

`CIIARLESP. WEBSTER. 

